1. Field of the Invention
The present invention relates to a method for forming a plurality of films, a method for fabricating an electron emitting element that employs those films, and a method for manufacturing an image forming apparatus that employs the electron emitting element.
2. Related Background Art
Conventionally, electron emitting elements are sorted into two types: a thermoelectron emitting element and a cold-cathode electron emitting element. The cold-cathode electron emitting element includes a field-effect emitting type (hereinafter referred to as an xe2x80x9cFE typexe2x80x9d), a metal/insulating layer/metal type (hereinafter referred to as an xe2x80x9cMIM typexe2x80x9d) and a surface conductive type. A well known electron emitting element of the FE type is disclosed in, for example, xe2x80x9cField Emission,xe2x80x9d W. P. Dyke and W. W. Doran, Advance in Electron Physics, 8, 89 (1956) or xe2x80x9cPhysical Properties of Thin-film field Emission Cathodes with Molybdeniumcones,xe2x80x9d C. A. Spindt, J. Appl. Phys., 47, 5248 (1976).
A well known electron emitting element of the MIM type is disclosed in, for example, xe2x80x9cOperation of Tunnel-Emission Devices,xe2x80x9d C. A. Mead, J. Appl. Phys., 32, 646 (1961).
A well known electron emitting element of a surface conductive type is disclosed in, for example, Radio Eng. Electron Phys., 10, 1290 (1965) by M. I. Elinson.
The electron emitting element of a surface conductive type supplies a current to a thin film, which is formed on a small area of a substrate that is parallel to the surface of the film, that emits electrons. Such electron emitting elements of a surface conductive type are the one disclosed above by Elinson that employs SnO2 thin film, one that employs Au thin film (Thin Solid Films, 9, 317 (1972), G. Dittmer), one that employs In2O3/SnO2 (IEEE Trans. ED Conf., 519 (1975), M. Hartwell and C. G. Fonstad), and one that employs a thin carbon film (Vacuum, Vol. 26, 1, page 22 (1983), Hisashi Araki, et al.).
In FIG. 17 is shown the arrangement of the element disclosed by M. Hartwell as a specific example of an electron emitting element of a surface conductive type. In FIG. 17, a substrate 1 and element electrodes 2 and 3 are provided for the emitting element. A thin conductive film 4 is a thin metal oxide film having a H-shaped pattern that is formed by sputtering, and an electron emitting portion 5 that is formed by an electrification process that is called electroforming, which will be described later. In FIG. 17, interval L between the element electrodes is set to 0.5 to 1 mm, and distance Wxe2x80x2 is set to 0.1 mm. The location and the shape of the electron emitting portion 5 are not fixed, and are specifically represented.
Generally, in a conventional electron emitting element of a surface conductive type, before the emission of electrons the electrification process called electroforming is performed for the thin conducive film 4, and the electron emitting portion 5 is formed. That is, the electroforming is the formation of the electron emitting portion by an electrification process. For example, a direct current voltage or a very gradually boosting voltage, such as 1 V/min., is applied to both ends of the thin conductive film 4 to locally destroy, or deform or degenerate the film 4, and the electron emitting portion 5 that electrically is highly resistant is formed. The electron emitting portion 5 emits electrons in the vicinity of a crack that occurs in one part of the thin conductive film 4. The electron emitting element for which the electroforming process has been performed applies a voltage to the thin conductive film 4 and permits the emission of electrons by the electron emitting portion 5.
Since the electron emitting element of a surface conduction type is easy to both form and arrange, multiple elements of this type can be formed and arranged in a large area. Therefore, various applications are being studied to determine the effective use of this characteristic. A load beam source and an image display device are examples of such applications.
In FIG. 18 is shown the arrangement of an electron emitting element disclosed in Japanese Patent Application Laid-Open No. 2-56822. In FIG. 18, the electron emitting element comprises: a substrate 1, element electrodes 2 and 3, a thin conductive film 4, and an electron emitting portion 5. Various methods are available for fabricating the substrate of the electron emitting element. For example, an ordinary vacuum deposition technique or photolithography technique is employed to form the element electrodes 2 and 3 on the substrate 1. Then, the thin conductive film 4 is formed by a dispersive coating method, following which a voltage is applied to the element electrodes 2 and 3, to electrify them and to form the electron emitting portion 5.
In addition, a further example is an electron source wherein multiple electron emitting elements of a surface conductive type are arranged in parallel to form multiple rows, and both ends (both of the element electrodes) of each electron emitting element are terminated by a wiring (also called a common wiring) e.g., Japanese Patent Application Laid-Open No. 64-1332, No. 1-283749 and No. 2-257552).
An example display device is proposed that can be fabricated so that it is as flat as a liquid crystal display device, but that is self-emitting and does not require a backlight. Such a display device comprises an electron source, wherein multiple electron emitting elements of a surface conductive type are arranged, and a fluophor that emits visible light upon irradiation with an electron beam originating at the electron source (U.S. Pat. No. 5,066,883).
The present inventor proposed a method, for fabricating an electron emitting element of a surface conductive type, that is advantageous for the formation of a conductive film to cover a large area, without resorting to the use of the vacuum sputtering method or the vacuum deposition method. According to another example method, an organic metal content solution is spinner-coated onto the substrate, and the film is patterned into a desired shape and is thermally cracked to form a conductive film. In addition, in Japanese Patent Application Laid-Open No. 8-171850 a method is proposed whereby, at a step in the patterning of a conductive film to provide a desired shape, droplets of an organic metal content solution are applied to the substrate using an ink-jet method, such as the bubble-jet method or the piezo-jet method, instead of the photolithography method, and a conductive film having a desired shape is formed.
According to the conventional ink-jet method described in Japanese Patent Application Laid-Open No. 8-171850, when wirings, an insulating layer and element electrodes can be fabricated as designed to form the substrate, the locations whereat it is determined the electron emitting portions are to be formed are arranged at intervals relative to a reference position on the electron source substrate. Therefore, when liquid droplets are ejected at a constant cyclic rate, as designed, they can be easily applied to the electron source substrate. However, in actuality, the widths and locations of the wirings and the insulating layer fabricated in or between the substrates by screen printing may vary. Thus, if the liquid droplets are applied as designed, when they contact the insulating layer and wirings they are absorbed, and no electron source is formed. Because of this defect, the resultant substrate can not fully satisfy the requirements for an electron source substrate.
According to the present invention, an innovative film formation method is provided. In particular, a method for accurately and efficiently forming a film is provided.
A film formation method according to one aspect of the present invention follows.
A method for forming a film locally on a substrate comprises the steps of:
detecting the state of the substrate;
employing the obtained result to calculate positional information concerning a plurality of locations at which the material for the film is to be provided to form the film; and
providing the material for the film at the plurality of locations based on the positional information that is obtained for the plurality of locations.
Using this method, a film can be formed efficiently.
Further, the present invention can be preferably employed when the film is a conductive film. And in addition, the present invention can be preferably employed when the film is composed of a material used to constitute an electron emitting element of a surface conductive type.
The state of the substrate that is detected is the state of a portion wherein the material is to be provided, or an area in the vicinity of the portion.
The state of the substrate that is detected concerns image information for the substrate. More specifically, the state is detected by image input means, such as a CCD camera.
The state of the substrate that is detected concerns the arrangement of components on the substrate.
The state of the substrate that is detected concerns the arrangement of electrodes on the substrate. The present invention can be preferably employed when the electrodes are electrically connected to a conductive film.
The state of the substrate that is detected concerns the arrangement of wirings on the substrate. The wirings, for example, are electrically connected to a film, in particular, to a conductive film. For the electric connection, another electrode may be located between the wirings and the conductive film.
The state of the substrate that is detected concerns the arrangement of an insulating layer on the substrate. The insulating layer is used to limit conductivity between the wirings on the substrate.
The state of the substrate that is detected concerns the arrangement of a common wiring to which a plurality of films, in particular, conductive films, are electrically connected, or of a member that accompanies the common wiring. The state wherein the common wiring or the accompanying member is arranged is detected, and based on this result, the positional information is obtained that concerns the locations at which the material is to be deposited for the conductive films that are to be connected to the common wiring. Therefore, the required positional information can be obtained even if not all the states have been detected that are concerned with the locations at which the conductive films are to be provided that are to be connected to the common wiring. In addition, the member that accompanies the common wiring is, for example, a member that complements the function of the common wiring. Such a member is an insulating member used to electrically isolate the common wiring.
The substrate is an insulating element.
The calculation of the positional information includes a calculation of information that concerns a location at which the material is to be provided.
The step of calculating the positional information for the locations includes a step of employing, to calculate positional information for each of the plurality of locations, the detected state of the substrate that concerns locations that are fewer in number than the plurality of locations. For example, positional information concerning a location at which the state of the substrate has not been detected can be calculated by employing the detection result concerning another location.
The calculation of the positional information includes the calculation of a compensation value that is used to compensate for a control value for controlling the locations whereat the material is to be provided. The control value is that used for controlling the relative locations of the substrate and a unit for providing the material. The compensation value is that used for compensating for a difference between the locations whereat the material has to be provided and locations whereat the material is to be provided when the compensation is not performed.
The material can be provided in liquid form. The material can be an organic metal solution. The material can be provided by an ink-jet device. The ink-jet device may be one for outputting a liquid using thermal energy, e.g., for using thermal energy to generate air bubbles in a liquid to output the liquid, or may be one for outputting a liquid using dynamic energy, i.e., for outputting a liquid using a piezoelectric element.
The material is sequentially provided at the plurality of locations.
The material is provided at the plurality of locations by the same provision unit.
The material is provided at the plurality of locations by a plurality of provision units.
The material is sequentially provided at the plurality of locations while the relative locations of the provision unit and the substrate are changed.
The material is sequentially provided at the plurality of locations at each of several locations for the plurality of locations.
The plurality of locations are preferably arranged in columns or in rows. The present invention is especially preferable when an arrangement includes a plurality of columns or rows.
The film formation method may include a step of annealing the material that is provided. A film may be stabilized by annealing.
The present application includes the following three inventions. The above described invention can be applied to the following three inventions.
A method, for forming a plurality of conductive films that are to be electrically connected to a common wiring, comprises the steps of:
detecting the arrangement state of the common wiring or of a member that accompanies the common wiring;
employing the obtained result to calculate positional information concerning a plurality of locations at which is to be provided a material for the plurality of conductive films that are to be electrically connected to the common wiring; and
providing at the locations, based on the positional information, the material for the conductive films.
This arrangement is preferable because, even when the states of the substrate that corresponds to all those locations are not detected, the positional information can be obtained for the locations at which the material for the conductive films is to be provided.
A method, for manufacturing an electron source including a plurality of electron emitting elements, comprises the steps of:
locally forming, on a substrate, conductive films that at least partially constitute the electron emitting elements, the step including
detecting the state of the substrate,
employing the obtained results to calculate positional information concerning a plurality of locations at which the material for the conductive films are to be provided to form the conductive films, and
providing the material for the conductive films at the plurality of locations based on the positional information that is obtained; and
forming an electron emitting unit in at least one part of each of the conductive films.
A method, for manufacturing an electron source having a plurality of electron emitting elements that are to be connected to a common wiring, comprises the steps of:
detecting the arrangement state of the common wiring or of a member that accompanies the common wiring;
employing the obtained result to calculate positional information concerning a plurality of locations at which is to be provided a material for the plurality of conductive films that are to be electrically connected to the common wiring;
providing at the locations, based on the positional information, the material for the conductive films; and
forming an electron emitting unit in at least one part of each of the conductive films.
According to the method for manufacturing an electron source, the step of forming the electron emitting unit includes a step of electrifying the conductive films. The electron emitting elements are electron emitting elements of a surface conductive type.